Electronic package structure and method

ABSTRACT

An electronic package structure and method use a conductive strip to bond die-to-die, die-to-lead, chip carrier-to-lead, or lead-to-lead. A conductive strip may carry greater current than a bonding wire, and thus may replace several bonding wires. The bonding of the conductive strip may be carried out by an SMT process, and thus requires lower cost than wire bonding processes. A conductive strip may be bonded to more than two dice or leads to save more bonding wires. A conductive strip is stronger than a bonding wire, and thus lowers the possibility of being broken.

RELATED APPLICATIONS

This application is a Divisional patent application of co-pendingapplication Ser. No. 12/068,773, filed on 12 Feb. 2008. The entiredisclosure of the prior application Ser. No. 12/068,773, from which anoath or declaration is supplied, is considered a part of the disclosureof the accompanying Divisional application and is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention is related generally to integrated circuit (IC)products and, more particularly, to an electronic package structure andmethod.

BACKGROUND OF THE INVENTION

In a typical semiconductor process, dice are cut from wafers by a dicingprocess, then each die is attached to a package substrate or a chipcarrier of a leadframe, the inputs/outputs of the die are electricallyconnected to leads of the leadframe by a bonding process, and finally,plastic, ceramic or metal is used to encapsulate the die except that theouter leads of the leadframe are left exposed outside the package forconnecting to other electronic components. This process is calledelectronic package method. With the protection of the electronicpackage, the IC components in the die may avoid damages from externalenvironment or forces.

For an electronic package, there are three popular bonding processes,wire bonding, tape automatic bonding (TAB) and flip-chip bonding, amongwhich the wire bonding is the most often used. The wire bonding processuses a bonder to bond one end of a wire to a bonding pad on a die andthe other end to a lead of a leadframe. The commonly used wires includealuminum wires, gold wires, silver wires and so on. The thickness of asingle wire or the number of wires will be proportional to the currentto be carried. The greater the current to be carried, the larger thethickness of a single wire or the number of wires is. For instance, forpower input and output of a power management chip, sometimes more thanfive bonding wires are bonded to a bonding pad of the chip because greatcurrent will flow therethrough. Such high current applications result inhigh cost and low yield packages. In some circumstances, for example, ifnon-uniform contact resistance is present between several wires bondedon a same bonding pad, or some of the bonding wires are broken, therewill be a single one among the bonding wires carrying the high currentand thus being broken.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electronic packagestructure for high current applications.

Another object of the present invention is to provide a strongerelectronic package structure.

Still another object of the present invention is to provide a low-costelectronic package structure and method.

According to the present invention, an electronic package structurecomprises a conductive strip to bond die-to-die, die-to-lead, chipcarrier-to-lead, or lead-to-lead.

A conductive strip may carry greater current than a bonding wire, andthus may replace several bonding wires.

The bonding of the conductive strip may be carried out by a surfacemounting technology (SMT). Preferably, the conductive strip is appliedwith a bonding material thereon and then bonded to a bump on a die.Alternatively, the bonding material is spotted or printed on a chipcarrier and a lead, and then the conductive strip is bonded to the chipcarrier and the lead. SMT process requires lower cost than wire bondingprocesses.

A conductive strip may be bonded to more than two dice or leads to savemore bonding wires.

A conductive strip is stronger than a bonding wire, and thus lowers thepossibility of being broken.

A conductive strip may easily replace bonding wires to carry greatercurrent no matter in single-chip packages and multi-chip packages.

The inventive method can be used together with conventional wire bondingprocesses, in which convention bonding wires are for small currentconducting, and conductive strips are for greater current conducting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment according to the present invention;

FIG. 2 shows a second embodiment according to the present invention;

FIG. 3 shows a third embodiment according to the present invention;

FIG. 4 shows a fourth embodiment according to the present invention;

FIG. 5 shows a fifth embodiment according to the present invention;

FIG. 6 shows a sixth embodiment according to the present invention;

FIG. 7 is a schematic view showing a conductive strip bonded to twodice; and

FIG. 8 is a schematic view showing a conductive strip bonded to a leadand a chip carrier.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first embodiment according to the present invention,which uses a conductive strip for a multi-chip package. Dice 16 and 18are attached on two portions of a chip carrier 12, a supporting frame 14supports the chip carrier 12, and a plurality of leads 10 surrounds thechip carrier 12. Bonding pads 162 and 182 are on the dice 16 and 18 andelectrically connected to the circuits in the dice 16 and 18,respectively. A conductive strip 20 is bonded to the bonding pads 162and 182 and thus electrically connects the dice 16 and 18 to each other.

FIG. 2 shows a second embodiment according to the present invention, inwhich dice 22, 24 and 26 are attached on three portions of a chipcarrier 12 and have bonding pads 222, 242 and 262 thereon, respectively,and a conductive strip 28 is bonded to the bonding pads 222, 242 and 262to electrically connect the dice 22, 24 and 26 to each other.

FIG. 3 shows a third embodiment according to the present invention,which uses a bonding wire and a conductive strip for an electronicpackage. A chip carrier 12 carries dice 30, 32, 34 and 36 on its fourportions respectively, and a conductive strip 38 is bonded to thebonding pads 322, 342 and 362 on the dice 32, 34 and 36 respectively.The conductive strip 38 is of a triangle shape to avoid the die 30. Abonding wire 40 is bonded by a conventional wire bonding process to thebonding pad 302 of the die 30 and the bonding pad 324 of the die 32.

FIG. 4 shows a fourth embodiment according to the present invention,which has dice 42 and 44 attached on a chip carrier 12 of a leadframe, aconductive strip 46 bonded to a lead 10 of the leadframe and a bondingpad 422 on the die 42, and another conductive strip 48 bonded to abonding pad 442 on the die 44 and another lead 48 of the leadframe.

FIG. 5 shows a fifth embodiment according to the present invention,which uses conductive strips for a single-chip package. A die 50 isattached on a chip carrier 12 of a leadframe, a bonding wire 52 isbonded to a bonding pad 502 on the die 50 and a lead 10 of theleadframe, a bonding wire 54 is bonded to another bonding pad 502 on thedie 50 and the chip carrier 12, and a conductive strip 56 is bonded toanother lead 10 of the leadframe and the chip carrier 12.

FIG. 6 shows a sixth embodiment according to the present invention, inwhich a bonding wire 62 is bonded to a bonding pad 582 on a die 58 and alead 10 of a leadframe, another bonding wire 60 is bonded to anotherbonding pad 582 on the die 58 and a chip carrier 12 of the leadframe,and a conductive strip 64 is bonded to two neighboring leads 10 of theleadframe.

The portions of a chip carrier for dice to be attached thereon may beelectrically connected to each other, for example in the case of a metalchip carrier; or they may be electrically insulated from each other, forexample in the case of a ceramic or plastic chip carrier.

As shown in the above embodiments, a conductive strip for electronicpackage structure and method according to the present invention may havevarious sizes and shapes based on their applications and may be bondedto several dice. In addition, in the above embodiments, although it isshown that the dice to be bonded by a conductive strip in an electronicpackage structure and method according to the present invention areattached on a same chip carrier, dice attached on different chipcarriers may be bonded by a conductive strip in some applicationsaccording to the present invention.

Preferably, the conductive strip used in an electronic package structureand method according to the present invention is a metal, such ascopper, silver and lead.

FIG. 7 is a schematic view showing a conductive strip bonded to two dicein an electronic package method according to the present invention. In atypical SMT process, solder paste is generally used as a bondingmaterial, and screen printing, needle spotting or dispensing is used toapply the bonding material to predetermined locations. The components tobe bonded are disposed on the solder paste at those locations, and thenheat treatment or UV light is applied to harden the solder paste so asto bond the components. In this embodiment, bumps 662 and 682 are grownon dice 66 and 68 in advance. Bonding material such as solder paste isapplied on a conductive strip 70, and then the conductive strip 70 isdisposed on the bumps 662 and 682 with the bonding materialtherebetween. After heat treatment, the bonding material, the conductivestrip 70 and the bumps 662 and 682 are eutectically solidified, and thusthe conductive strip 70 and the bumps 662 and 682 are bonded together.

FIG. 8 is a schematic view showing a conductive strip bonded to a leadand a chip carrier in an electronic package method according to thepresent invention. Bonding material 76 is applied on a lead 72 and achip carrier 74 at predetermined locations by spotting or dispensing,and then the conductive strip 70 is disposed on the lead 72 and the chipcarrier 74 with the bonding material 76 therebetween. After heattreatment, the bonding material, the conductive strip 70, the lead 72and the chip carrier 74 are eutectically solidified. In addition,printing may be used instead, to apply the bonding material 76 on thepredetermined locations. The bonding material 76 may be other thansolder, for example conductive glue or silver glue.

While the present invention has been described in conjunction withpreferred embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and scopethereof as set forth in the appended claims.

1. An electronic package method comprising the steps of: providing a diehaving a bonding pad thereon and a lead of a leadframe; and bonding aconductive strip to the bonding pad and the lead.
 2. The electronicpackage method of claim 1, further comprising the step of attaching thedie on a chip carrier of the leadframe.
 3. The electronic package methodof claim 1, wherein the step of bonding a conductive strip to thebonding pad and the lead comprises the steps of: applying a bondingmaterial on the conductive strip, or on the bonding pad and the lead;disposing the conductive strip on the bonding pad and the lead with thebonding material therebetween; and heat treatment for bonding theconductive strip to the bonding pad and the lead with the bondingmaterial.
 4. The electronic package method of claim 3, wherein thebonding pad has a bump thereon, and the conductive strip is bondedthereon.
 5. The electronic package method of claim 1, wherein the stepof applying a bonding material on the conductive strip, or on thebonding pad and the lead comprises the step of printing or spotting thebonding material on the conductive strip, or on the bonding pad and thelead.